优化: 前端扫描文案 i18n + parseStack 抽公共 + alert/confirm 换组件

- 扫描/目录状态文案走 $t（Projects/ProjectDetail，zh-CN+en 同步）
- parseStack 抽公共到 src/utils/project.ts（删两份本地实现）
- 8 处原生 alert/confirm 全换（confirm→ConfirmDialog / alert→Arco Message），控制流语义不变

Sprint 20 审查 ⑥⑦⑧。vue-tsc 0 error，验证 safe 0 issue

src/i18n/en/projectDetail.ts

@@ -48,6 +48,13 @@ export default {
     relocateDir: 'Relocate',
     bindDir: 'Bind Directory',
     dirStatusLabel: 'Directory Status',
+    dirChecking: 'Checking…',
+    dirExists: '✓ Directory exists',
+    dirMissing: '⚠ Directory moved, recommend relocate',
+    dirConflict: 'This directory is already bound to project "{name}"',
+    relocateConfirmRelocate: 'Relocate project directory to:\n{dir}\n\nTech stack will be re-detected. Confirm?',
+    relocateConfirmBind: 'Bind project directory to:\n{dir}\n\nTech stack will be re-detected. Confirm?',
+    relocateFailed: 'Relocate failed: {msg}',
     // Tech stack
     techStackLabel: 'Tech Stack',
   },